Magnetic tape cassettes used in video cassette recorders include a pair of tape reels mounted in the cassette housing. Typically, these cassettes include a device which places a downward axial force on the tape reels to maintain proper position and rotation of the tape reels, particularly as the cassette is loaded into the recorder. Some cartridges use reel springs mounted on the upper housing of the cassette and other cassettes use axial pressure buttons mounted in the upper housing of the cassette. Betacam-L type cassettes, for example, use pressure buttons.
FIG. 1 illustrates a known hold-down or reel pressure button assembly. This button assembly requires a plurality of components. The button assembly 10 is mounted within an opening 12 in the window 14 of the cassette upper housing wall. The button assembly 10 is mounted over the axial center of a tape reel 16 with an inner button 18 contacting the tape reel 16. The inner button 18 includes a central horizontal portion 20 on which a cylindrical upwardly extending portion 22 is mounted. Two opposing openings 24 are formed in the central horizontal portion 20 inside of the cylindrical upwardly extending portion 22. Two opposing recesses 26 are formed in the inside surface of the cylindrical upwardly extending portion 22 adjacent the openings 24. A cylindrical downwardly extending portion 28 is formed on the lower surface of the central horizontal portion 20 and has a larger diameter than the upwardly extending portion 22. The downwardly extending portion 28 terminates in a circular horizontal flange 30.
A wear pad 32 can be mounted to the tape reel 16 to provide a contact surface with the inner button 18. The wear pad 32 provides a surface of high lubricity and wear resistance. A button cap 34 is mounted within the cylindrical upwardly extending portion 22 and includes two downwardly extending legs 36 which extend through the two openings 24 in the central horizontal portion 20 of the inner button 18. Each leg 36 terminates in an outwardly facing tab 38 which is received in a respective recess 26 in the inner button 18 to frictionally lock the button cap 34 to the inner button 18. A coil spring 40 is mounted around the inner button 18 and between the window 14 and the circular horizontal flange 30 of the inner button 18.
While this configuration adequately performs its intended purpose, it has numerous drawbacks. The multiple part assembly is relatively complex in design and is difficult and expensive to manufacture and assemble. The button cap 34 can relatively easily disengage from the inner button 18 and damage the assembly 10. Moreover, in the event of failure of the frictional lock between the button cap tabs 38 and the inner button recesses 26, the disengaged button cap 34 can damage the cassette recorder or create a flying missile safety hazard if it disengages while the cassette is being handled.